World first – Audi’s twin turbo diesel gets electric compressor assistPOSTED BY Nigel Andretti ON 04 March 2016
IN a world first, Audi has introduced a diesel-engined S model to its Q7 model line that uses an electric compressor to cut turbo-lag to its two turbo chargers.
The newly developed 4.0-liter V8 diesel delivers 435hp and 900Nm of torque with estimated NEDC fuel consumption of 7.4 litres of fuel per 100 km, corresponding to CO2 emissions of 194 grams per kilometer.
The SQ7 accelerates from 0 to 100 km/h in 4.8 seconds and top speed is 250 km/h.
The car also has supporting 48V subsytem for the elctric compressor.
The two turbo chargers operate in squence with with one turbo operating at low and intermediate load. The second activated at higher loads. The electric-powered compressor (EPC) augments the work of the two turbochargers, particularly in the lower engine speed range, providing for dynamic off-the-line performance.
The EPC — a first in a production vehicle — is placed in the air path downstream of the intercooler, close to the engine. Because the EPC does not require any exhaust-gas energy to develop boost, it can be used at any time, thus making it the solution for the traditional weaknesses of the classic exhaust-gas turbocharger.
It comes into play in less than 250 milliseconds making lag almost non-existent.
Audi is also using its valvelift system for the diesel engine — inlet and exhaust cam shafts each have two cam contours per valve.
On the inlet side, one cam contour supports starting off in conjunction with the EPC, while the other optimises cylinder filling and thus power at high engine speeds. The AVS system on the exhaust side enables activation of the second exhaust-gas turbocharger.
The biturbo V8 combined with the EPC is a core element of the global Audi diesel strategy. With high torque even at low engine speeds and low consumption figures, it is ideally suited for global markets.
Audi offers the SQ7 TDI with an optional driving dynamics package comprising three technology modules: sport differential, electromechanical active roll stabilization and all-wheel steering.
The highly integrated suspension control unit is used in the SQ7 TDI. It assumes the central control of the adjustable shock absorbers, the air springs, the sport differential and roll force distribution. By bundling all relevant suspension functions into a central control unit, the developers achieved an optimal networking and coordination of the functions among themselves.
The electromechanical active body roll stabilisation uses a compact electric motor with a three-stage planetary gearbox separating the two halves of the stabiliser.
On an uneven road surface, they are actively decoupled from one another, resulting in improved ride comfort, the company said.
During sporty driving, the tubes are interconnected and twisted against each other. That significantly reduces body roll, i.e. the lean of the car. Together with the transmission, the electric motors produce anything up to 1,200 N·m (885.1 lb?ft) of torque. The effect is taut, sporty handling—the car leans less in bends and the tendency to understeer is further reduced.
The front and rear stabilisers can be adjusted independently of each other offering high levels of steering precision and the agility of the car.
All-wheel steering. With all-wheel steering, the rear wheels turn in by as much as five degrees, making parking easier. The more direct front-axle steering ratio of the SQ7 TDI improves the handling characteristics. Depending on the situation, the rear wheels steer opposite or in the same direction as the front wheels, improving dynamics and stability.
The car is a seven-seater with S body styling, 20-inch alloy wheels, all-LED headlights and full suite of cockpit electronic controls including MMI navigation plus with MMI Touch, adaptive S air suspension, Audi pre sense city and a powered tailgate fitted as standard.
“Following the launch of the successful SQ5, we are now also applying the concept of a diesel-engined S model to the Q7 model line.
“So equipped, the SQ7 TDI with a V8 TDI engine achieves the consumption figures of a six-cylinder. The new technology solution of the electric powered compressor in the SQ7 TDI is a world first in the competitive environment, with which Audi once again underscores its claim Vorsprung durch Technik,” said Dr Stefan Knirsch, Member of the Board of Management of AUDI AG for Technical Development.
The Audi SQ7 TDI is the lightest SUV in its segment, yet makes no compromises with respect to crash safety. The body features an innovative multimaterial construction. Hot-shaped and extremely strong sheets form the backbone of the occupant cell; the outer skin is made of aluminium. The centre of mass is low – another factor for the immersive handling. The drag coefficient is an outstanding 0.34.